Is there a way to quick toggle cameras?
It's possible with a little addon:

bl_info = {
    "name": "Cycle Cameras",
    "author": "CoDEmanX",
    "version": (1, 0),
    "blender": (2, 65, 0),
    "location": "View3D &gt; Ctrl + Shift + Left/Right Arrow",
    "description": "Switch scene camera to next or previous camera object",
    "warning": "",
    "wiki_url": "",
    "category": "3D View"}

import bpy

class VIEW3D_OT_cycle_cameras(bpy.types.Operator):
    """Cycle through available cameras"""
    bl_idname = "view3d.cycle_cameras"
    bl_label = "Cycle Cameras"
    bl_options = {'REGISTER', 'UNDO'}

    direction = bpy.props.EnumProperty(
        name="Direction",
        items=(
            ('FORWARD', "Forward", "Next camera (alphabetically)"),
            ('BACKWARD', "Backward", "Previous camera (alphabetically)"),
        ),
        default='FORWARD'
    )

    def execute(self, context):
        scene = context.scene
        cam_objects = [ob for ob in bpy.data.objects if ob.type == 'CAMERA']

        if len(cam_objects) == 0:
            return {'CANCELLED'}

        try:
            idx = cam_objects.index(scene.camera)
            new_idx = (idx + 1 if self.direction == 'FORWARD' else idx - 1) % len(cam_objects)
        except ValueError:
            new_idx = 0

        context.scene.camera = cam_objects[new_idx]
        return {'FINISHED'}


addon_keymaps = []

def register():
    bpy.utils.register_module(__name__)

    wm = bpy.context.window_manager
    kc = wm.keyconfigs.addon
    if kc:
        km = wm.keyconfigs.addon.keymaps.new(name='3D View', space_type='VIEW_3D')
        kmi = km.keymap_items.new(VIEW3D_OT_cycle_cameras.bl_idname, 'RIGHT_ARROW', 'PRESS', ctrl=True, shift=True)
        kmi.properties.direction = 'FORWARD'
        addon_keymaps.append((km, kmi))
        kmi = km.keymap_items.new(VIEW3D_OT_cycle_cameras.bl_idname, 'LEFT_ARROW', 'PRESS', ctrl=True, shift=True)
        kmi.properties.direction = 'BACKWARD'
        addon_keymaps.append((km, kmi))

def unregister():
    for km, kmi in addon_keymaps:
        km.keymap_items.remove(kmi)
    addon_keymaps.clear()
    bpy.utils.unregister_module(__name__)


if __name__ == "__main__":
    register()


An operator to cycle through available camera objects is bound to CtrlShiftLeft Arrow to go to (alphabetically) previous camera and CtrlShiftRight Arrow to go to next camera.